The invention relates to a rotor for a reluctance machine, to an electrical machine having such a rotor and also to a method for manufacturing the said rotor. The rotor has a laminated core with a number of rotor core plate layers insulated electrically from one another. Each rotor core plate can have strip-shaped flux-conducting portions for conducting the magnetic flux between d-axes of the rotor. The flux-conducting portions extend in their longitudinal extent at an angle or transverse to a respective q-axis of the rotor and are separated from one another by flux barriers.
Such a rotor for a reluctance motor is known from U.S. Pat. No. 5,818,140 A. This document describes a rotor, of which the laminated core consists of rotor core plates having punched-out sections. This rotor is also referred to here as a Vagati rotor. Air is located between the individual flux-conducting sections in the flux barriers created by the punched-out sections, which acts as a magnetic flux barrier. The punched-out sections lead to a weakening of the mechanical stability of the laminated core however, so that the described rotor is not suitable for high speeds, in particular is not suitable for speeds of greater that 3,000 rpm. For this reason rotors of the type described are not suitable where a high speed is required.
A Vagati rotor is known from JP 2002 095227 A, in which the flux barriers are encapsulated with a casting compound made of artificial resin. The radially adjacent flux-conducting portions in the invention have trapezoidal-shaped cutouts, into which the artificial resin likewise flows during casting. Through this the flux-conducting portions are then connected via a dovetail connection with the hardened artificial resin. At high speeds a tensile force caused by gravitational forces is redirected in this way from the outer circumference of the rotor via the artificial resin inwards towards the shaft. The disadvantage here is that the trapezoidal-shaped cutouts in the flux-conducting portions adversely affect the efficiency of the motor, since the magnetic flux is impeded. A tensile force is also applied to the artificial resin by the arrangement, which can lead to a break or a crack in the artificial resin.
The continued use of permanent magnets in the rotor is known as a construction principle of a reluctance rotor, in order to obtain a hybrid rotor type comprising a reluctance and synchronous motor. M=3/2 p(p*Iq+(Ld−Iq)*Id*Iq) is produced as the mechanical torque M created by the rotor, wherein p specifies the number of pole pairs, P specifies the additional field-linked direct axis flux created by the permanent magnets, Iq specifies the q component of the coil current of the stator, Id specifies the d component of the coil current of the stator, Lq specifies the q component of the rotor inductance and Ld specifies the d component of the rotor inductance.
The arranging of permanent magnets in a reluctance rotor has a number of disadvantages. The permanent magnets are generally manufactured as cubes or blocks, which are then inserted into the laminated core of the reluctance rotor. To this end the flux barriers in which the permanent magnets are to be arranged must have a shape with corners to enable the permanent magnets to be accommodated and retained. In that the air barriers are adapted to the shape of the permanent magnets with the lowest possible variance in the shape of the permanent magnets, they are no longer optimally adapted to the field profile of the magnetic flux, as is needed to realize a Vagati rotor. Furthermore the permanent magnets are not able to be arranged without gaps in the curved flux barriers, so that there are gaps, which are filled with air, present between the permanent magnets. Furthermore the permanent magnets are not able to be arranged without gaps in an angled laminated core along the axially curved passages or tunnels arising from this arrangement, since, for inserting the mostly square permanent magnets the dimensions of said magnets, depending on the helix angle, must be smaller than the flux barriers. This leads to a loss of efficiency.
A reluctance rotor, in the flux barriers of which a permanently magnetic material is arranged, is described in document WO 2009/063350 A2. The permanently magnetic material can be arranged in a plastic matrix and the flux barriers can have been filled with it by an injection-molding process. By means of the material an end disk can also be molded in each case onto axial end surfaces of the rotor, in order to stabilize the rotor. By shaping the plastic matrix an imbalance of the rotor can be compensated for.